Via an analysis of noun phrases and the distribution of nouns and determiners in a Spanish–English corpus, this paper illustrates the compatibility of recent minimalist proposals with the Matrix Language Frame model of codeswitching, that recognizes an asymmetry between the participating languages. The demand for the Matrix Language to provide an abstract grammatical frame in bilingual constituents ties in with the type of uniformity that Chomsky (2001) regards as necessary for the explanatory study of language and language variation.